Nemophora decisella (Walker, 1863)

Liao, Cheng-Qing, Hirowatari, Toshiya, Yagi, Sadahisa, Wang, Min, Wang, Xing & Huang, Guo-Hua, 2023, The fauna of the family Adelidae (Insecta, Lepidoptera, Adeloidea) from China, Zootaxa 5348 (1), pp. 1-152 : 36-37

3.8 Nemophora decisella species group

Diagnosis. This species group can be characterized by the following features: the male eyes are very large, close to each other dorsally; the base of antennae is stout with thickened scales, especially in female adult; the forewing has bright metallic luster, a conspicuous transverse central fascia placed in the middle, usually red, orange, or yellow; the foretibiae are covered with dense thickened scales apically; the ventral base of valvae is fused medially; the sacculus is expanded to form an angular process; and the apex of aedeagus is curved dorsally, with a pair of developed hook-shaped carinae near the apex laterally.

Remarks. Eight species belong to the decisella species group, namely N. decisella ( Walker, 1863) , N. paradisea ( Butler, 1881) , N. smaragdaspis (Meyrick, 1924) , N. cantharites (Meyrick, 1928) , N. heteroxantha Diakonoff, 1951 , and N. arcuatifasciata sp. nov., N. caeruliantenna sp. nov. and N. xizangensis sp. nov. as new species herein. Among them, N. cantharites occurs in the Philippines and N. heteroxantha in Java, but Kozlov & Robinson (1996a) considered that N. heteroxantha to be probably a synonym of N. decisella . The other four species have been recorded in China. Male adults of the decisella group have dominant large eyes, which may be closely related to the swamming behavior of adelid moths ( Hirowatari & Nagaike 1998; Hirowatari et al. 2012). In addition, the decisella group differs from other species groups by the typical and conspicuous sexual dimorphism, not only in the antenna (length, color and morphology) and compound eyes (size in male), but also in the forewing color pattern (almost completely yellow in the forewing base of females, but the same color as the ground in males).

Key to species of the decisella group based on external morphology and male genitalia

1 Antenna basally with metallic blue scales.............................................. N. caeruliantenna sp. nov.

- Antenna basally without metallic blue scales................................................................ 2

2 Forewing transverse central fascia obviously arcuate outward at middle, which slightly form “3”-shaped................................................................................................ N. arcuatifasciata sp. nov.

- Forewing transverse central fascia broad, with almost straight margins........................................... 3

3 Forewing central fascia narrow, placed between basal 1/3 to 1/2; apex of valva distinctly rounded; transtilla narrower in lateral part, base of median process obviously narrow...................................................... N. decisella

- Forewing central fascia distinctly broad, placed between basal 1/3 to 2/3; apex of valva almost acute; transtilla wider in lateral part, base of median process broad........................................................................ 4

4 Ground color of forewing and thorax both metallic brass; forewing transverse central fascia yellowish; uncus with a distinct median keel; vinculum relatively slender, length about 5.2 × width..................................... N. paradisea

- Ground color of forewing and thorax both metallic blue or green; forewing transverse central fascia orange-red; uncus only with a weak median keel; vinculum relatively broad, length 4.2–4.4 × width........................................... 5

5 Forewing transverse central fascia with outward curved margins; apex of valva digitate, slightly beyond uncus; anterior part of suspensorium at same level of posterior margin of vinulum........................................ N. smaragdaspis

- Forewing transverse central fascia with almost straight margins; apex of valva pointed, not beyond uncus; anterior part of suspensorium far beyond posterior margin of vinculum...................................... N. xizangensis sp. nov.